[libvirt-users] Qemu backend: Cannot start new domains after some time

Hi, After using libvirt+qemu for a while, I'm finding that I can no longer reliably start new domains. Most of the time when I try, I'm getting this, or something like it: virsh # start dhcpv6server error: Failed to start domain dhcpv6server error: monitor socket did not show up.: No such file or directory The same thing happens when trying to start the domain using the C-API. This happens particularly often when there are any domains running that are using a lot of CPU, even when most of the physical cores of the host machine are still sitting idle. (I've created a number of Linux VMs, with one CPU core each, that do nothing but calculate primes in an endless loop for load-testing purposes.) If I destroy all of the high-load domains, I can usually start up new domains again. The time between requesting the domain startup and the error message being printed varies greatly, from less than a second to more than a minute. The host machine is running Fedora 12 with libvirt 0.8.1 and qemu-kvm 0.12.4. Any ideas what might be causing this, and what can be done about it? It would be a big problem for us if we cannot start any new domains just because some of the existing ones are using a lot of CPU... Regards, Guido